Photolithographic fabrication of semiconductor components, such as integrated circuits and dynamic random access memory chips, is customary in the semiconductor industry. In photolithographic fabrication, light may be used to cure or harden a photomask that is used to form a pattern of conductive, semiconductive, and insulative components in the semiconductor layer. The resulting pattern of conductive, semiconductive, and insulative components on the semiconductor layer form extremely small microelectronic devices, such as transistors, diodes, and the like. The microelectronic devices are generally combined to form various semiconductor components.
The density of the microelectronic devices on the semiconductor layer may be increased by decreasing the size or geometry of the various conductive, semiconductive, and insulative components formed on the semiconductor layer. This decrease in size allows a larger number of such microelectronic devices to be formed on the semiconductor layer. As a result, the capability and speed of the semiconductor component may be greatly improved.
The lower limit on the size, often referred to as the line width, of a microelectronic device is generally limited by the wavelength of light used in the photolithographic process. The shorter the wavelength of light used in the photolithographic process, the smaller the line width of the microelectronic device that may be formed on the semiconductor layer. Semiconductor component fabrication may be further improved by increasing the intensity of the light used in the photolithographic process, which reduces the time the photomask material needs to be radiated with light. As a result, the semiconductor components may be produced faster and less expensively.
Extreme ultraviolet (EUV) light has a very short wavelength and is preferable for photolithographic fabrication of semiconductor components. Conventional systems for generating EUV light typically include an energy source impinging on a hard target. The energy source may be a high energy laser, an electron beam, an electrical arc, or the like. The hard target is generally a ceramic, thin-film, or solid target comprising materials such as tungsten, tin, copper, gold, xenon, or the like. Optics, such as mirrors and lenses, are used to reflect and focus the EUV light on a semiconductor layer.
Conventional systems and methods for generating EUV light suffer from numerous disadvantages. One of these disadvantages is that debris from the energy source/target interaction is produced along with the EUV light. The production of debris, which increases with the intensity of the energy source, results in the target being degraded and eventually destroyed. The debris may coat and contaminate the optics and other components of the system, thereby reducing efficiency and performance while increasing frequency of maintenance and length of down time.
Recent improvements in systems and methods for generating EUV light include an energy source impinging on a fluid target. However, these systems and methods also suffer from disadvantages. One disadvantage is the existence of plasma-induced erosion. The energy source impinging on the fluid target produces a plasma which can degrade the external surfaces of the components of the light source. This plasma-induced erosion releases contaminants that must be removed, adding cost and complexity to the system.
Another disadvantage is that the plasma is a major source of high heat loading on the components of the light source. Thermal particle or ion impact from the plasma further adds to the high radiative heat load on the components. This problem is compounded by the fact that the amount of heat that can be removed from the components is limited by their severe geometric restrictions.
Yet another disadvantage is caused by the collection optics needing a direct view of the plasma to collect the light rays being generated. This results in direct plasma interaction on the collection optics which causes erosion. The optics are sensitive to erosion and costly to repair.